Towards the end of the summer the waters around southern Rhode Island get quite sparkly at night. I’ve wondered for a while what exactly the sparkling things might be, but it wasn’t until recently that I remembered to bring a bucket with me and look at its contents in the light of day.

When I went out to the ocean a couple of weeks ago, I noticed three distinct sizes of glowing creatures; the tiny specks that make a cloud when you kick the water, the medium ones that look like a pair of triangles, and the big circular ones, that stay glowing for a second or two.

Steve Haddock, one of our friends at the bioluminesence lab at the Monterey Bay Aquarium Research Insitute, helped characterize some of these organisms. Here’s what I found.

The larger circular ones are comb jellies.

We get a lot of comb jellies called Mnemiopsis around here. By the end of the summer there are sometimes so many that it feels like swimming in a giant bubble tea. This seems to be a very young Mnemiopsis, not quite mature yet. Comb jellies don’t have any stinging cells, and are not technically jellyfish– corals and anemones are more closely related to jellyfish than these creatures are, even though these look similar. For more about the psychedelic rainbow colors pulsing down the side of this animal, check out Brown undergrad Lee Stevens’ podcast on comb jellies.

According to Dr. Steve Haddock, bioluminesence correspondent, the smallest size of glowing thing is most probably a bunch of single celled organisms called dinoflagellates.

The last glowing group I found seems to be these copepods, a type of small crustacean.

The appendages at the very back of their bodies are long and thin, but move back and forth so fast that they look like little paddles. These thin appendages whipping around are probably what looked little triangles underwater.